The present invention pertains to a flow detecting mechanism and, more particularly, to a flow detecting mechanism useful for operating other mechanisms such as a switch.
Flow responsive switch mechanisms of the type referred to have many varied applications for sensing and controlling flow in fluid carrying apparatus as well as operating associated structure in response to the presence or absence of fluid flow. Many such switches now available sense fluid flow by movement of a vane or like detector disposed in a fluid carrying conduit. Physical movement of the detector is accomplished either directly by fluid flow impinging thereon or by use of structure such as orifices, blades or turbines in the conduit that creates a pressure differential which causes shifting of the detector. This physical movement must then be transmitted externally of the conduit to operate a switch, usually electrical, to indicate the presence of flow.
A typical example of such flow responsive switch mechanisms is that described in U.S. Pat. No. 3,845,259 issued Oct. 29, 1974. As described in this patent, a shaft pivots at a single point in response to a fluid flow to actuate a switch. This type of device has been shown to be useful when detecting flow in pipes of a relatively large diameter, for example, diameters of greater than 2". However, it has been found that with only a single pivot point, sufficient force cannot be generated when detecting flows in pipes having a diameter from 3/4 to 11/2". It has also been found that with the smaller diameter pipes, the fluid flow has tendency to bypass the actuator thus making it more difficult to pivot the shaft and actuate a switch.